Electrotherapy machine

ABSTRACT

A machine for inducing sleep and other therapy effects by means of repetitive electrical pulses wherein potential danger to the treated subject is avoided by the generation of trains of rapid alternately positive and negative pulses whose vectorial sum is equal to zero, thus avoiding the application of net direct currents. Trains of pulses are applied to the subject through a transformer to avoid shock hazard. A timer attenuator allows gradual rise in current over a fixed time period to a fixed level, maintenance of the fixed current level for a variable time period which may be set, and gradual decline in current over a fixed time period.

Unite States Patent [19] Holt et al.

[ Feb. 27, 1973 [54] ELECTROTHERAPY MACHINE OTHER PUBLICATIONS Inventors: William J- Holt, Garland, -I Radio -Electronics, Feb. 1965, PP. 4042.

8" y de la Tour, L05 Angel, Amer. Journ. of Med. Electronics, Jan.-Mar., 1965, Calif- PP. 39-41. [73] Assignee: Neuro Systems Inc., Garland, Tex. Electronics May 1963 20-21- Electronics World, Sept., 1963, PP. 27-29. [22] Filed: March 26, 1970 [21] Appl. No.: 22,809 Primary Examiner-Kyle L. Howell Attorney-Olson, Trexler, Wolters and Bushnell Related U.S. Application Data 5 [63] Continuation-impart of Ser. No. 629,232, April 7, [57] ABSTRACT 1967 abandoned A machine for inducing sleep and other therapy effects by means of repetitive electrical pulses wherein (g1. ..128/1 (k6ll2jll h2ull potential danger to the treated Subject is avoided by [58] i 419423 the generation of trains of rapid alternately positive and negative pulses whose vectorial sum is equal to [56] References Cited zero, thus avoiding the application of net direct currents. Trains of pulses are applied to the subject UNITED STATES PATENTS through a transformer to avoid shock hazard. A timer 2 004 751 5/1935 Fischer et al 128/420 X attenuator allows gradual rise in current over a fixed 1:257:55 2/1918 Vreeland..... ....128/422 time Period a fixed level maimemmce of the fixed 3,050,695 8/1962 Duvall ..128/421 x current level for a variable time period which y be 2,838,672 6/1958 Paust ..l28/422 X set, and gradual decline in current over a fixed time 3,160,159 12/1964 Hoody et al. ..l28/1 C period. 3,255,753 6/l966 Wing ..l28/42l 3,388,699 6/1968 Webb et a]. ..l28/1 7 Claims, 11 Drawing Figures I- HIGH P08. I 2 l II POWER oi/OJ l2 RELAXATION TIMER SOURCE )3? OSCILLATOR ATTENUATOR Low MONOSTABLE MULTIVIBRATOR 8 9 ELECTRODES 4 TO SUBJECT GATE NEG. 5 IO RETURN MANUAL OSC'LLATOR ATTENUATOR LIMITED POWER AMPLIFIER ISOLATION TRANSFORMER PATENTEB 3,718,132

SHEET 19F 4 VOLTS F|G.l FIG. 2

PRIOR ART HIGH Pos. l I I 2 II ay POWER '2 RELAXATION TIMER SOURCE 23; OSCILLATOR ATTENUATOR LOW A A P08. 1 3

MONOSTABLE MULTIVIBRATOR 8 9 ELECTRODES 4 F TO SUBJECT GATE use. 5 IO RETURN OSCILLATOR MANUAL o-----p ATTENUATOR LIMITED -----9 POWER Q AMPLIFIER 7 FIG. 3 INVENTORS:

WILLIAM J. HOLT ROGER BOY d8 [0 TOUR W ISOLATION TRANSFORMER ATTORNEY PATENTEDFEBZYIQYK 3,718,132

SHEET 2 0F 4 .w no a o N N INVENTORS WILLIAM J. HOLT N I) m ROGER BOY de lo TOUR m E? 0 g 8 BY 'L'ikzz i 1 "2' ATTORNEY P/WIMTEIJ 3.718.132

SHEET 3 BF 4 FIG. 5

FIG. 6

INVENTORS: WILLIAM J. HOLT ROGER BOY de lo TOUR PATENTEIJFEBZYIEIB SHEET U UF 4 FIG. IO

IO 2O 3540 505560 POT ROTATION IN MINUTES FIG. 8

FIG.9

I VARIABLE t INVENTORS WILLIAM J. HOLT ROGER BOY de lo TOUR ATTORNEY FIG ELECTROTI-IERAPY MACHINE This application is a continuation-in-part of our prior application, Ser. No. 629,232 filed April 7, 1967, now abandoned.

This invention relates to a machine which induces sleep and other therapy effects by the application of repetitive electrical pulses to the head of a subject. The repetitive electrical pulses generated are trains of rapid alternately positive and negative pulses whose vectorial sum is equal to zero.

The inducement of sleep by means of repetitive electrical pulses applied to the head of a subject is well known in the art. Many instruments have been manufactured in the United States and abroad, particularly in the Soviet Union, the United Kingdom, and Japan to generate electrical pulses for application to the head. All of these prior art generators, however, have one disadvantage in common: they are potentially dangerous to the subject. The primary danger, in addition to the shock hazard of those generators utilizing vacuum tubes, is a result of the single polarity pulse output to the subject provided by these prior art generators.

These single polarity pulses produce an electrolytic dissociation in the living cells. No matter how minute the pulses, the cumulative action of the numerous pulses can lead to an irreversible damage to the brain.

This invention provides a pulse generator which does not apply any single polarity component to the subject, thus avoiding any electrolytic action and concomitant damage to the brain. Instead of single polarity pulses, the sleep inducing machine of this invention generates trains of rapid pulses, alternately positive and negative, such pulses having a vectorial sum of zero.

The trains of pulses produced by the generator of this invention are applied to the subject through a transformer, so that no conductive path exists between the generator and the subject. This isolation avoids any potential shock hazard.

An additional safety feature of the subject sleep inducing machine is that the instantaneous output power to the subject is limited to a value which is safe to humans. Any malfunction or fault in the system results in reduced or no output power, rather than in a maximum power output as is generally the case with prior art sleep inducing machines.

An object of this invention is the provision of an electrotherapy machine which generates trains of rapid pulses, alternately positive and negative, such pulses having a vectorial sum equal to zero.

Another object of this invention is to provide a machine which is not dangerous to the subject.

An additional object of this invention is to provide a sleep inducing machine which avoids any electrolytic action.

Still another object of this invention is to provide a sleep inducing machine which avoids any potential shock hazard.

Yet another object of this invention is to provide a sleep inducing machine whose instantaneous output power to the subject is limited to a safe value.

A further object of this invention is to provide a sleep inducing machine in combination with a timer attentuator which allows a gradual rise in current over a fixed period of time to a fixed level, maintenance of the fixed current level for a variable time period which may be set, and a gradual decline in current over a fixed time period.

Other objects and advantages of this invention will be particularly set forth in the claims and will be apparent from the following description, when taken in connection with the accompanying drawings, in which:

FIG. 1 is a wave form diagram of the single polarity pulse output of prior art devices.

FIG. 2 is a wave form diagram of the trains of rapid pulses, alternately positive and negative produced by the generator of the present invention.

Fig. 3 is a block diagram of the sleep inducing machine of the invention.

FIG. 4 is a schematic circuit diagram of one embodiment of the sleep inducing machine of the invention.

FIG. 5 is a front view of a recommended timer for the sleep inducing machine.

FIG. 6 is a side view of the timer taken along the line 5-5 of FIG. 5.

FIG. 7 is a graph showing the current time function achieved by the timer of FIGS. 5 and 6.

FIG. 8 is a diagrammatic representation showing the arrangement of the resistive elements of the potentiometers.

FIG. 9 is a diagrammatic representation showing the arrangement of the potentiometers when the knob is set at 40 minutes.

FIG. 10 is a diagrammatic representation showing the wiper arms moving in phase over a 40 minute setting.

FIG. 11 is a diagrammatic representation showing the wiper arms moving in phase over a 60 minute setting.

The sleep inducing machine of the invention is comprised of the elements as shown in FIG. 3 which operate as follows:

A direct current power source 1 provides energy to the transistor circuits composing the pulse generator. The direct current power source I as shown in FIGS. 3 and 4 has both a high and a low positive side and a minus or zero potential side. The terms high and low are relative indicating merely that the high side has a higher output voltage than the low side. In one embodiment the high positive side is 12 volts at 3 ma., the low positive side is 3 volts at 3 ma., and the minus side is at zero potential. Applicant's invention may be constructed with a power source having only one positive output voltage rather than the two positive outputs or power supplies of the power source of the embodiment of FIGS. 3 and 4, and applicant does not intend to limit the invention to a power source having two positive outputs. The transistor circuits are a relaxation oscillator 2 which provides a recurrent signal to a monostable multivibrator 3. The monostable multivibrator 3 can be adjusted to generate a pulse of a given duration every time it receives a signal from the relaxation oscillator 2. A gate 4 is open during the duration of the pulse. While the gate is open it connects the power source 1 to the oscillator 5 and the limited power amplifier 6. The output of the oscillator 5 is a wave train of constant amplitude and of a frequency which is adjustable between set limits. The duration of the wave train is the duration of the pulse produced by the multivibrator 3. The output of the oscillator 5 is connected through limiting resistors to a push pull amplifier 6. The power output of the push pull amplifier 6 is limited to a set number of milliwatts instantaneous. Through an isolation transformer 7, the pulse trains are fed to the two electrodes 8 and 9 which are applied to the subject. The signal produced by prior art devices is shown in FIG. 1. FIG. 2 shows the signal produced by the present invention. The strength of the signal is adjustable through a manual attenuator 10. The timer attenuator 11 provides an adjustment whereby the signal current advances slowly over a fixed period of time to a maximum level at which it is maintained for an adjustable period of time after which the signal current is slowly reduced to zero over a fixed period of time.

FIG. 4 is a schematic circuit diagram of one embodiment of the sleep inducing machine of the invention within the scope of FIG. 3. Integrated circuits (double NCR gates) are utilized for simplicity and reliability.

The relaxation oscillator is composed of a unijunction transistor together with a time constant circuit comprising a variable resistor 21 for a continuous adjustment of the repetition rate, a resistor 22 and three capacitors 23, 24, and for selection of the ranges of adjustment through a selector switch 26. A resistor 27 compensates for ambient temperature variations.

The output signal of the relaxation oscillator is developed across the load resistor 28 and applied to one input of the double gate 29. The output of that particular gate to which the output signal of the relaxation oscillator is applied is connected to the input of its twin gate through a timing circuit including switch 30, resistors 31 and 32 and capacitor 33. The output of the double gate 29 is connected to a solid state switch, NPN transistor 34, through a limiting resistor 35.

The NPN transistor 34 connects or disconnects the return of the output circuit to or from the minus side of the power source 1. The maximum current that the NPN transistor 34 can carry is controlled by the value of resistor 35. This is one of the two circuits which limit the instantaneous output power of the sleep inducing machine to a safe value.

The output circuit is composed of an oscillator and a push-pull amplifier. The output circuit could be simplified by using an oscillator connected directly to the subject; but with the omission of the push-pull amplifier, the output could not be as accurately controlled.

The oscillator is basically a double gate 36 in which each input is connected by means of the time constant circuits to the output of the other gate. The time constant circuits include resistors 37, 38, 40, and 41, switch 39, and capacitors 42 and 43.

The outputs of the two gates comprising double gate 36 are connected by means of limiting resistors 44 and 45 to a push-pull amplifier including NPN transistors 46 and 47 and transformer 48. The primary of transformer 48 is shunted by capacitor 49. The resistors 44 and 45 limit the input current and as a result limit the output power developed by the transistors 46 and 47 for a given voltage. The resistors 44 and 45 comprise the second built-in security mechanism to limit the instantaneous power applied to the subject to a safe limit.

The secondaries of the isolation transformer 48 feed three different circuits as follows:

I. The output circuit to the electrodes 8 and 9 which are applied to the subject. The output voltage is controlled by the switch 50 and the potentiometer 51.

2. The neon lamp 52 circuit, the neon lamp 52 being in series with a limiting resistor 53 to provide a visual stimulus, and

3. The loudspeaker 54 circuit which provides an auditory stimulus.

in compliance with a specific embodiment of the present invention, the components heretofore described were selected to take the values or designations set forth in Table I below.

TABLE I Component Value or Designation transistor 20 2N2646 variable resistor 21 500K ohm potentiometer resistor 22 K ohms capacitor 23 2 mfd.

capacitor 24 0.5 mfd.

capacitor 25 0.1 mfd.

resistor 27 270 ohms resistor 28 100 ohms gate 29 Fairchild pl 914 resistor 31 2.7 K ohms resistor 32 2.7 K ohms capacitor 33 l mfd.

transistor 34 2N3565 resistor 35 3.9 K

gate 36 Fairchild pl 914 resistor 37 5.6 K ohms resistor 38 5.6 K ohms resistor 40 5.6 K ohms resistor 41 5.6 K ohms capacitor 42 0.05 mfd.

capacitor 43 0.05 mfd.

resistor 44 22 K ohms resistor 45 22 K ohms transistor 46 2N3565 transistor 47 2N3565 transformer 48 core: 3/16' 'x3/ 16"Perrnalloy or l-li-Nickel primary: 600 turns CI, No. 44 wire secondary: 900+900+900 turns, No. 44 wire; 50 turns. No. 44 wire.

potentiometer 51 50 K ohms neon lamp 52 NIB-2 resistor 53 220 K ohms loudspeaker 54 3.2 ohms In the specific embodiment outlined with respect to the values and designations set forth in Table I, the power supply was selected to be plus 12 volts on the high positive side and plus 3 volts on the low positive side. In addition, the timer attenuator 11 was selected to comprise a Type 0-100UA direct current ammeter connected across the center of a diode bridge employing four 1N93 diodes, a filtering capacitor having a rating of 100 mfd. being connected in parallel with the meter.

It has become apparent that the sleep inducing machine is most effective when the current to the subject is advanced slowly over a period of time. Through tests a period of approximately 5 minutes has been found to be ideal. After attaining the maximum current level, the signal is maintained at such level for a period of time depending on how long sleep is desired to be induced. At the expiration of the period during which the signal is maintained at maximum current level, it has been found to be most effective to reduce the current slowly to zero. Through tests it has been found to be desirable to reduce the signal current from maximum to zero over a period of 5 minutes. The timer shown in FIGS. 5 and 6 embodies one device for performing these functions. In addition the timer of FIGS. 5 and 6 provides one meansfor varying the time of maximum current flow from zero to the maximum time of 50 minutes.

Referring to FIG. 5, a front view of the timer is shown. FIG. 6 shows a side view. The timing element 60 is a conventional escapement timer of the type commonly used in mechanical kitchen timers. It can be wound by hand to a predetermined time whereupon it will return to zero after that time period has elapsed. Fastened to the winding shaft 61 of the timing element 60 are two potentiometers 62 and 63. Potentiometer 62 is fastened to the base member 64 by means of bracket 65 and nut 66. Wiper arm 67 moves directly with the shaft 61 of the timing mechanism 60. Associated with potentiometer 62 is toggle switch 68. This toggle switch 68 becomes operative when the time setting winding knob 69 is moved off of the zero point at which time the toggle switch 68 turns on the direct current power to the sleep inducing machine. Toggle switch 6% serves the same function of switch 12 of FIGS. 3 and 4.

The second potentiometer 63 is mounted on the shaft 61 of the timer mechanism 60, but is free to rotate about the shaft 61. The wiper arm 71, however, is fastened rigidly to the shaft 61 and rotates in phase with wiper arm 67. Fastened rigidly to potentiometer 63 housing 70 is a cylindrical member 72 which forms a bearing for shaft 61 but which also has an appendage 73 which serves as an indicator and a method for rotating the potentiometer 63 housing 70 relative to the shaft 61. Indicator 73 and potentiometer housing 70 are prevented from rotating freely about shaft 61 by a constant spring pressure supplied by a spring 74. Spring 74 presses against the case 75 of the instrument thus exerting a clutch force between member 73 and case 75. Since indicator 73 and potentiometer 70 are rigidly fastened together, these elements do not move relative to each other.

The current time function is shown in FIG. 7 where it can be seen that the current increases linearly from zero to maximum in 5 minute period and decreases linearly from maximum to zero in a 5 minute period. The time period of the maximum current is a variable which can be set by the operator of the sleep inducing machine. The elements of potentiometers 62 and 63 are special elements as shown in FIG. 6. For 30 of their rotation they are essentially linear potentiometers. For the balance of their rotation they are low resistances elements. The low resistance ends of the elements are connected together electrically. in order to provide a variable time period for the maximum current to flow it is necessary that the relative positions of the high resistance elements 79 and 77 of potentiometers 62 and 63 be changed. See FIGS. Q, 10 and II. The changing of the relative positions of the high resistance elements 79 and 77 can be done as follows:

Stop 76 which is fastened to potentiometer 70 as shown in FIG. 9 is engaged by wiper arm 71. as shaft 61 is rotated to wind the timer mechanism 60.

FIG. 9 shows the potentiometer arrangements when the knob 69 has been set to 40 minutes. Under this condition the potentiometer housing 70 has been rotated with wiper arm 71 engaging stop 76. indicator 73 will then be at 30 minutes which will be the time period of maximum current. Indicator 73 remains in the position at which it has been set as knob 69 rotates back to zero.

The potentiometer assembly serves as an attenuator for the current. Thus at the start of the 40 minutes shown in FIG. 9, wiper arm 71 contacts the maximum resistance part of potentiometer 63, namely high resistance element 77. Wiper arm 67 contacts the low resistance part of potentiometer 62, namely low resistance element 76. See also FIG. 10. Thus, if the potentiometer high resistance elements 77 and 79 are each assumed to have a resistance of 50,000 ohms, the maximum resistance of 50,000 ohms will occur between terminals 86 and 81 at the start of the 40 minute cycle. As the timer knob 69 rotates toward zero, wiper arm 71 rotates in a counterclockwise direction along high resistance element 77 and in a 5 minute period will contact low resistance element 82. Thus after 5 minutes have expired wiper arms 71 and 67 are essentially shorted together with a direct connection and there is no attenuation to the current. This condition exists until the final 5 minute interval is reached at which time wiper arm 67 engages high resistance element 79 and as the time progresses toward zero the maximum resistance of high resistance element 79 is placed in the circuit. Under these conditions the resistance between terminals 80 and 81 will be 50,000 ohms when wiper arm 67 reaches zero.

It can be seen in FIG. ill that the same sequence described above will take place if the timer mechanism 60 is wound to the full 60 minutes. Potentiometer housing and indicator 73 would then be rotated to 50 and would remain there until manually moved. The operator can return indicator 73 to zero manually after each use, or he can return it to the time which he wishes the machine to be at its maximum current.

Toggle switch 68 is a conventional radio type toggle switch which cuts off after the shaft 61 has been returned to zero position. With indicator 73 and knob 69 in the positions shown in FIG. 5, the shaft is in its zero position.

Timers other than the one outlined above may be used with the sleep inducing machine of this invention as timer attenuators. The above is given only as representative of one suitable timer.

By making the maximum resistance elements cover arcs of more or less than 30 degrees of rotation the time of increase from zero to maximum current and the time of decrease from maximum to zero current can be made to be periods of time more or less than 5 minutes depending on what time period is found to be most desirable for a particular application. The increase and decrease time periods can of course be different where this is determined to be desirable by making the two maximum resistance elements of different degrees of arc.

A timer attenuator can also be used which will allow present fluctuations of current during the running of the sleep inducing machine.

While the invention has been described in relation to certain preferred embodiments thereof, it nevertheless will be apparent to those skilled in the art that certain modifications may readily be made within the scope of the principles disclosed. Therefore, it is intended that the scope of the invention be defined and limited only by the appended claims.

What i claim as my invention and desire to secure by Letters Patent of the United States is:

11. An electrotherapy device comprising: electrode means adapted to be attached to a subject; first circuit means operating to produce a train of electric pulses; second circuit means connected to and cooperating with said first circuit means for producing a train of periodic bursts of alternating current, each of said bursts having a vectorial sum equal to zero, whereby to avoid impressing net direct current on a treated subject, said second circuit means connected in electrical communication with said electrode means and adapted to deliver said bursts of alternating current to said subject whereby to provide electrotherapeutic treatment; a direct current power source, said second circuit means comprising gate means connected to said power source and to said first circuit means, said gate means being operated by electric pulses from said first circuit means and operating to pass pulses of power from said source, said second circuit means further comprising oscillator means connected to said gate means for receiving said pulses of direct current power and operating to produce said train of periodic bursts of alternating current.

2. An electrotherapy device according to claim 1 which further comprises power limiting means connected to said oscillator means for restricting the power gain between pre-selected limits.

3. An electrotherapy device comprising: a power source; a pulse generator receiving energy from the power source and producing cursent pulse trains whose vectorial sum is equal to zero whereby to avoid impressing net direct current on a treated subject; and electrode means adapted to apply the current pulse trains to a subject, said pulse generator including a relaxation oscillator connected to the source of power, means connected to the relaxation oscillator and to the power source, said means being adjustable to generate a pulse of a given duration every time it receives a signal from the relaxation oscillator, a gate which is open during the duration of the pulse, said gate being connected to both the positive and negative sides of the power source and to the pulse generator, an oscillator which is connected to the gate and which is connected to the negative side of the power source through the gate when the gate is open, said oscillator being also connected to the positive side of the power source and said oscillator having an output which is a wave: train of constant amplitude and a frequency which is adjustable, the duration of the wave train being the duration of the pulse produced by the pulse generating means, means for amplifying the output of the oscillator, the oscillator and amplification means together constituting the output circuit, and means adapted to feed the amplified pulse train output of the oscillator to the subject, said means adapted to feed the amplified pulse train output of the oscillator to the subject being an isolation transformer having its primary connected to the means for amplifying the oscillator output and its secondary connected to said electrode means, said electrotherapy device further including manual attenuator means for adjusting the strength of the output signal, said manual attenuator means being connected between the secondary of the isolation transformer and the electrode means, and timer attenuator means connected between the manual attenuator means and the electrode means, the timer attenuator means enabling the output current signal to be advanced over a set period of time until the maximum current signal is reached, and maintaining the maximum current signal for an adjustable period of time afgir which the timer attenuator reduces the current sign to zero over a set period of time.

4. An electrotherapy device according to claim 3 in which the relaxation oscillator includes a unijunction transistor and a time constant circuit including a variable resistor for a continuous adjustment of the repetition rate, said variable resistor being connected at one of the ends to the power source; a resistor, said resistor being connected at one of its ends to the other end of the variable resistor and at its other end to the emitter electrode of the unijunction transistor; a selector switch having capacitors for selection of the ranges of adjustment connected to the emitter electrode of the unijunction transistor; a resistor to compensate for ambient temperature variations, said resistor being connected between the power source and the base 2 electrode of the unijunction transistor; and a load resistor connected to the base 1 electrode of the unijunction transistor, the output signal of the relaxation oscillator being developed across said load resistor.

5. An electrotherapy device according to claim 3 in which the gate is a double gate having the output signal of the relaxation oscillator applied to one of its inputs, the output of the particular gate connected to the output signal of the relaxation oscillator being connected to the input of its twin gate through a timing circuit, and theoutput of the double gate being connected to a solid state switch which connects and disconnects the retum of the output circuit to and from the minus side of the power source.

6. An electrotherapy device according to claim 5 in which the output of the double gate is connected to the solid state switch through a resistor which limits the maximum current that the switch can carry thereby limiting the instantaneous output power to a safe value.

7. An electrotherapy device according to claim 3 in which the oscillator is a double gate having the input of each of its gates connected by means of time constant circuits to the output of the other gate, with the output of each gate being connected to a limiting resistor, said limiting resistors limiting the input current and thus the output power developed by the means for amplifying the output of the oscillator for a given voltage, said limiting resistors thus limiting the instantaneous output power to a safe limit.

l 1 i l 4! 

1. An electrotherapy device comprising: electrode means adapted to be attached to a subject; first circuit means operating to produce a train of electric pulses; second circuit means connected to and cooperating with said first circuit means for producing a train of periodic bursts of alternating current, each of said bursts having a vectorial sum equal to zero, whereby to avoid impressing net direct current on a treated subject, said second circuit means connected in electrical communication with said electrode means and adapted to deliver said bursts of alternating current to said subject whereby to provide electrotherapeutic treatment; a direct current power source, said second circuit means comprising gate means connected to said power source and to said first circuit means, said gate means being operated by electric pulses from said first circuit means and operating to pass pulses of power from said source, said second circuit means further comprising oscillator means connected to said gate means for receiving said pulses of direct current power and operating to produce said train of periodic bursts of alternating current.
 2. An electrotherapy device according to claim 1 which further comprises power limiting means connected to said oscillator means for restricting the power gain between pre-selected limits.
 3. An electrotherapy device comprising: a power source; a pulse generator receiving energy from the power source and producing current pulse trains whose vectorial sum is equal to zero whereby to avoid impressing net direct current on a treated subject; and electrode means adapted to apply the current pulse trains to a subject, said pulse generator including a relaxation oscillator connected to the source of power, means connected to the relaxation oscillator and to the power source, said means being adjustable to generate a pulse of a given duration every time it receives a signal from the relaxation oscillator, a gate which is open during the duration of the pulse, said gate being connected to both the positive and negative sides of the power source and to the pulse generator, an oscillator which is connected to the gate and which is connected to the negative side of the power source through the gate when the gate is open, said oscillator being also connected to the positive side of the power source and said oscillator having an outPut which is a wave train of constant amplitude and a frequency which is adjustable, the duration of the wave train being the duration of the pulse produced by the pulse generating means, means for amplifying the output of the oscillator, the oscillator and amplification means together constituting the output circuit, and means adapted to feed the amplified pulse train output of the oscillator to the subject, said means adapted to feed the amplified pulse train output of the oscillator to the subject being an isolation transformer having its primary connected to the means for amplifying the oscillator output and its secondary connected to said electrode means, said electrotherapy device further including manual attenuator means for adjusting the strength of the output signal, said manual attenuator means being connected between the secondary of the isolation transformer and the electrode means, and timer attenuator means connected between the manual attenuator means and the electrode means, the timer attenuator means enabling the output current signal to be advanced over a set period of time until the maximum current signal is reached, and maintaining the maximum current signal for an adjustable period of time after which the timer attenuator reduces the current signal to zero over a set period of time.
 4. An electrotherapy device according to claim 3 in which the relaxation oscillator includes a unijunction transistor and a time constant circuit including a variable resistor for a continuous adjustment of the repetition rate, said variable resistor being connected at one of the ends to the power source; a resistor, said resistor being connected at one of its ends to the other end of the variable resistor and at its other end to the emitter electrode of the unijunction transistor; a selector switch having capacitors for selection of the ranges of adjustment connected to the emitter electrode of the unijunction transistor; a resistor to compensate for ambient temperature variations, said resistor being connected between the power source and the base 2 electrode of the unijunction transistor; and a load resistor connected to the base 1 electrode of the unijunction transistor, the output signal of the relaxation oscillator being developed across said load resistor.
 5. An electrotherapy device according to claim 3 in which the gate is a double gate having the output signal of the relaxation oscillator applied to one of its inputs, the output of the particular gate connected to the output signal of the relaxation oscillator being connected to the input of its twin gate through a timing circuit, and the output of the double gate being connected to a solid state switch which connects and disconnects the return of the output circuit to and from the minus side of the power source.
 6. An electrotherapy device according to claim 5 in which the output of the double gate is connected to the solid state switch through a resistor which limits the maximum current that the switch can carry thereby limiting the instantaneous output power to a safe value.
 7. An electrotherapy device according to claim 3 in which the oscillator is a double gate having the input of each of its gates connected by means of time constant circuits to the output of the other gate, with the output of each gate being connected to a limiting resistor, said limiting resistors limiting the input current and thus the output power developed by the means for amplifying the output of the oscillator for a given voltage, said limiting resistors thus limiting the instantaneous output power to a safe limit. 